In wood constructions for residential houses, a concrete foundation is poured and set, and then a wooden sill is secured (e.g. anchor bolts) to the top of the walls of the foundation. The posts are then placed on top of the wooden sill and secured by nails or other suitable fasteners. In some constructions, the wooden sills are cut to provide mortises for receiving the lower tenon ends of the posts to increase the strength of the wall construction.
In the past, residential houses where constructed with heavy tile roofing. Due to the heavy load transmitted from the roof through the posts to the foundation walls or ground sills, the posts where securely supported thereon. However, the construction of new wooden residential homes have replaced the heavy tile roofing with roofing materials which are significantly lighter. This makes the upper structure of the construction lighter reducing the strength of the joints with respect to sideways movement of the posts relative to the sills. Specifically, the posts carry less of a load reducing the shear stress between the joints between the bottom surface ends of the posts and the upper surfaces of the sills allowing the wall to be shifted laterally under a lighter side load such as applied by wind or earth quake.
For these reasons, in situation of this new type of residential construction being hit by a strong wind pressure such as generated by a typhoon, wind blast, or even by a big earthquake, it is possible that the construction can even be severely damaged or destroyed because the position of the posts on the foundation walls can be easily moved out of place or shifted, especially if the posts are directly placed on the foundation walls.
Today many three-story houses are being built to use the limited amount of land effectively. The three-story houses are typically taller than the conventional two-story houses, thus, the three-story houses are less stable than the two-story houses. In order to build three-story houses on very small building areas, the foundation must be specially constructed to withstand continuous and transient loads.
The method of construction involving connecting tenon ends of posts inserted into mortises cut into wooden sills is somewhat problematic. For example, it is difficult to fasten the posts on the centerline of the wooden sills; the designated positions to fasten the posts on the wooden sills may change slightly from the original design making it difficult to insert the tenons of the posts properly into the mortises in the wooden sills, and thus possibly requiring the mortises on the wooden sills to be reformed.